JPH11315954A - Motor valve actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously variably detect output torque in a mounted state irrespective of a motor structure. SOLUTION: In a motor valve actuator for transmitting a motive force from a motor 1 through a worm reduction mechanism 2 to the valve shaft of a valve, the worm shaft 6 of the worm reduction mechanism 2 is provided with a differential transformer 9 for continuously detecting a thrust direction changing position ΔL and taking this out as a voltage signal Vx. Thus, an optional point is used for system control, and also used for maintenance by continuous monitoring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric valve actuator for driving an electric valve for system automation used in petroleum complexes, chemical plants, power plants and the like.

[0002]

2. Description of the Related Art In a petroleum complex, a chemical plant, or the like, a large number of valves are provided in each part of a pipe. In many cases, an electric valve actuator is attached to these valves in order to automate the system. In this case, proper setting and maintenance of the valve are indispensable, but output torque of the valve shaft of the valve is detected for the purpose of setting torque and diagnosing valve deterioration.

[0003]

By the way, in the conventional torque detection, attention is paid to the fact that the worm shaft causes a thrust displacement corresponding to the output torque, and a predetermined displacement of the worm shaft is detected by a limit switch. Alternatively, the output torque of the motor alone is calculated by detecting the current value of the motor and the coil magnetic flux density, and the output torque is calculated by the product of this and the reduction ratio (experimental value) of the reduction mechanism. .

[0004] However, in the former case, the output torque is measured using a test stand or the like in an electric valve actuator assembly factory, and the operating point of the limit switch is set so that the limit switch operates at a predetermined output torque. Need to adjust. For this reason, there is a problem that the adjustment requires skill, and it is difficult to adjust the output torque at the site because the output torque is not known, or there is a problem that the output torque can be detected only at one point and the resolution is low. . On the other hand, in the latter case, the structure of the motor itself is limited to that capable of calculating such an output torque, so that it cannot be applied to an electric valve actuator using a motor (for example, a DC motor) other than the induction motor. There are difficulties.

[0005]

In order to solve the above problems, the present invention relates to an electric valve actuator for transmitting power from a motor to a valve shaft of a valve via a worm reduction mechanism. Wherein the worm shaft is provided with detecting means such as a differential transformer for continuously detecting the amount of displacement in the thrust direction and extracting the displacement as an electric signal.

With such a structure, the amount of displacement of the worm shaft in the thrust direction can be considered to be theoretically proportional to the output torque of the worm wheel, that is, the valve shaft of the valve. If the directional displacement is extracted as an electric signal by a detecting means such as a differential transformer, the output torque of the valve stem of the valve can be continuously monitored by the electric signal. Therefore, any point can be used for system control. In addition, since electric signals corresponding to the thrust displacement amount are continuously taken out, adjustment of the seating point, the overload point, and the like can be easily performed in the mounted state. In particular, since the displacement amount resolution of the worm shaft is high, accuracy such as torque setting can be expected. Further, since the torque detection method does not depend on the structure of the motor, it can be used for an electric valve actuator having any motor structure.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. The electric valve actuator of this embodiment is
The driving force from the motor 1 is transmitted to a center column (not shown) via the worm speed reduction mechanism 2, thereby driving the valve shaft of the valve. The worm reduction mechanism 2 supports the worm shaft 6 in both ends of the housing 3 via a pair of bearings 4, and connects the bearing 4 to an axially inner end surface 3 a formed in the housing 3. The spring is elastically biased toward the center position via a disc spring 7 elastically provided. A worm wheel 8 is meshed with a central portion of the worm shaft 6 with its axis orthogonal to the center.
When the worm shaft 6 is rotationally driven, the rotational power is converted into orthogonal rotational power of the worm wheel 8.

In such a configuration, in the present embodiment, a differential transformer 9 as a detecting means of the present invention is provided on the other end side of the worm shaft 6. This differential transformer 9
Is a normal type including a core 10 made of a magnetic material attached to the other end of the worm shaft 6 and a coil portion 11 disposed in a position surrounding the core 10 in an annular shape.
When the coil portion 11 has a primary coil 11a at the center in the thrust direction and secondary coils 11b on both sides thereof, when a voltage is applied to the primary coil 11a through the power supply circuit 12,
When the core 10 is displaced in the thrust direction with respect to the center position of the coil portion 11, a voltage Vx proportional to the displacement ΔL can be taken out between the terminals 11c and 11d of the secondary coil 11b.

That is, in the electric valve actuator of this embodiment, when the worm shaft 6 is rotationally driven by the rotational power of the motor 1, the worm shaft 6 is converted into the rotational operation of the worm wheel 8, and the valve shaft of the valve is rotated by a center column (not shown). It will be driven. At this time, due to the load resistance of the valve, as the driving torque T0 of the worm wheel 8 increases, the worm shaft 6 receives a force in the thrust direction due to the reaction force thereof, and compresses the disc spring 7 in accordance with the spring characteristics of the disc spring 7 while thrusting. In the direction .DELTA.L. Then, in the differential transformer 9, this displacement amount ΔL
Can be taken out between the terminals 11c and 11d.

With such a configuration, the amount of displacement ΔL of the worm shaft 6 in the thrust direction and the output torque T0 of the valve shaft of the valve can be continuously monitored with the voltage Vx of the differential transformer 11. Therefore, any point can be effectively used for system control. In addition, since the electric signal Vx corresponding to the thrust displacement amount ΔL can be continuously taken out, adjustment of a seating point, an overload point, and the like, and torque setting can be easily performed in a state where the local plant is mounted. In particular, since the worm shaft 6 has a high displacement amount resolution, it is possible to ensure accuracy in torque setting and the like by simple work. In addition, since the output state of the electric valve actuator can be constantly monitored, the progress of valve deterioration can be checked in advance based on whether seating torque is properly generated at a certain point, and maintenance can be performed in advance. It can also be used for self-diagnosis and data logging. Further, since the torque detection method does not depend on the structure of the motor, it can be used in an electric valve actuator having any motor structure.

The specific configuration of each section is not limited to the illustrated embodiment. For example, in the above embodiment, the case where the differential transformer is used as the detecting means for continuously detecting the thrust displacement amount of the worm shaft has been described. However, even if a capacitance type displacement sensor is used, an effective effect can be obtained. Can be. As other displacement sensors, various displacement sensors such as a linear potentiometer, a photoconductive element, an eddy current type, a Hall element, and a semiconductor magnetic resistance element can be used. Further, the position where the displacement sensor is provided may be basically any thrust position on the worm shaft, and other configurations may be variously modified without departing from the spirit of the present invention.

[0012]

According to the present invention having the above-described structure, torque detection can be performed electrically continuously and accurately even when mounted on a plant or the like, and the detection does not depend on the type of motor or the like. It will be. For this reason, it can be applied regardless of the type of motor, and the torque setting can be performed easily and accurately.Also, the output status of the electric valve actuator is constantly monitored to be useful for maintenance in advance and to be effectively used for system control. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Worm reduction mechanism 6 ... Worm shaft 11 ... Detection means (differential transformer)

Claims (1)

[Claims] 1. An electric valve actuator for transmitting power from a motor to a valve shaft of a valve via a worm speed reduction mechanism, wherein a displacement in a thrust direction is continuously detected by a worm shaft of the worm speed reduction mechanism to generate an electric signal. An electric valve actuator characterized by comprising a detection means for taking out as a sensor.